The protein Shadoo (Sho) is a paralogue of prion protein, and encoded by the gene Sprn. Like prion protein it is primarily expressed in central nervous system, and has been shown to have a similar expression pattern in certain regions of the brain. We have generated reporter mice carrying a transgene encompassing the Sprn promoter, exon 1, intron 1 and the 5'-end of exon 2 driving expression of either the LacZ or GFP reporter gene to study the expression profile of Shadoo in mice. Expression of the reporter genes was analysed in brains of these transgenic mice and was shown to mimic that of the endogenous gene expression, previously described by Watts et al. [1]. Consequently, the Sprn-LacZ mice were used to study the spatial expression of Sho in other tissues of the adult mouse. Several tissues were collected and stained for beta-gal activity, including the thymus, heart, lung, liver, kidney, spleen, intestine, muscle, and gonads. From this array of tissues, the transgene was consistently expressed only in specific cell types of the testicle and ovary, suggesting a role for Shadoo in fertility and reproduction. These mice may serve as a useful tool in deciphering the regulation of the prion-like gene Sprn and thus, indirectly, of the Shadoo protein. (C) 2011 Elsevier Inc. All rights reserved.